Dakota Gas conducts seismic surveys at carbon dioxide storage site

Dakota Gasification Company, partnering with Denver, Colorado-based Carbon Vault, conducted seismic surveys for its Broom Creek carbon dioxide (CO₂) injection field in early November near Beulah, North Dakota.

The survey is part of the permitting process for Dakota Gas, a subsidiary of Basin Electric Power Cooperative, to store CO₂ underground. It started injecting it at the site in February.

Three large trucks – called vibroseis trucks – were used in the surveys. These trucks send low-frequency vibrations, or seismic waves, deep into the earth where they bounce off the geological rock layers before rising to the surface where data is collected.

 “These vibrations help in mapping the subsurface layers, providing valuable data for various applications,” said Kurt Dutchuk, pipeline superintendent at Dakota Gas.

Rhonda Gathers, vice president of Engineering and Operations at Carbon Vault, said in addition to being able to see the subsurface rock layers, they can compare new data with the baseline data obtained before CO₂ started to be injected into the site. “We’re basically looking to see that the carbon dioxide stays within the permitted area and doesn’t migrate outside of it.”

Dakota Gas is permitted to store roughly 26 million metric tons of carbon dioxide over 12 years in the Broom Creek formation. Since February, the company has sent about 1.3 million metric tons of CO₂ underground. 

Seismic surveys are required for storage sites during years one, three, five and 10. Although Dakota Gas is just shy of the one-year mark sequestering CO₂ in the Broom Creek formation, Dutchuk said the company wanted to survey the site before the snow flies.

“Winter months can present significant challenges for these operations,” he said. “When deep snow or mud is present, access to the survey lines can be difficult, as the weight and size of vibroseis trucks can cause them to get stuck or make it impossible to travel through the terrain.”

Data obtained from the survey is still being analyzed. Once verified, it is sent to a processing facility, with results available anywhere from four to eight weeks.

“Despite its large presence in the field for a week in November, the seismic surveys are only a small part of the CO₂ testing and monitoring program,” Gathers said. “The testing and monitoring program, as a whole, ensures that the geologic storage project is operating safely and protecting all underground sources of drinking water.”